Computing

56 ◾ Computing

Each letter α will be represented by the pair of letters indicating the

row and column in which α lies in the matrix above. For example, the

representations of A, B, M, N, Y, and Z are AA, AB, CB, CC, ED, and

EE, respectively. e plaintext “Let us build ships” is encrypted to

CAAEDDDEDCABDEBDCAADDCBCBDCEDC. e Roman alphabet

version of the Polybius system is monoalphabetic substitutions into the

target alphabet {AA, AB, AC, AD, AE, BA, BB, …, EE}.

One of the earliest encryptions by monoalphabetic substitutions

appears in the Kama Sutra, a group of texts written in the fourth century

in India. Mallanaga Vatsyayana was a Hindu ...